Do you want to know your ‘body burden’?

Measuring the chemicals within through biomonitoring

By Dolon Chakravartty and Robyn Lee

We are exposed to both naturally occurring and commercially produced toxic substances in a variety of ways every day. We may inhale them, swallow them in contaminated food or water, or in some cases, absorb them through our skin. Recent research indicates that all human beings carry varying amounts of chemicals in our bodies, with health effects that are not yet known. Each person’s risk of developing health problems related to environmental chemicals is tied to a combination of exposure, genetics, sex, age, nutrition and lifestyle. And an individual’s exposure to environmental pollution can be analyzed through a process called “biomonitoring.”

As analytical methods become more sophisticated, we are able to detect minute amounts of chemical presence in human tissue. A number of studies have used biomonitoring techniques to determine levels of chemicals in the body and concerns have emerged around disclosing results. While some argue that reporting results of the presence of chemical substances causes unnecessary alarm, others advocate for the right to know, even if the possible health effects are unclear. This raises ethical issues related to reporting biomonitoring results to study participants.

Biomonitoring, a scientific technique for assessing human exposures to natural and synthetic chemicals, is based on sampling and analysis of a person’s tissues and fluids. It measures contact with and absorption of toxic chemicals in the body through detection in human blood, urine, semen, amniotic fluid, breast milk, saliva, breath, hair, fingernails or other tissue. Samples are analyzed by assessing the concentration of the “parent chemical” and the products created when the “parent” breaks down (metabolites), as well as the products that the parent chemical reacts with. In this way, biomonitoring results are a detailed measure of exposure from multiple sources and routes.

“Body burden”—also called the internal or absorbed dose—is the amount of chemical compound present in the human body at a given point in time.

Biomonitoring was originally used to detect exposure to chemicals in occupational settings, but its use became more widespread during the 1970s through the detection of lead levels in the blood linked with leaded gasoline, lead paint and lead solder in canned food. This method for assessing exposure has recently become less expensive and more widely available with advances in molecular biology that have allowed for more specific, sensitive and biologically relevant tests. With these advances, biomonitoring research is becoming more common in academic and governmental settings, as well as in environmental advocacy and research organizations that use these studies to promote more stringent regulation of toxic chemicals.

However, because little is known about the potential health related outcomes of many of the pollutants studied, there are ethical challenges regarding whether and how to report results to individual study participants when clinical effects are uncertain.

Nationwide studies and sources

In the United States, the Centers for Disease Control and Prevention began a nationwide biomonitoring study in 1999, which is now updated every few years. Two major national biomonitoring studies are currently underway in Canada. The Canadian Health Measures Survey (CHMS) carried out by Health Canada and Statistics Canada includes a biomonitoring component. The CHMS is a population-based household survey that is currently assessing 91 chemicals and their metabolites in a Canadian sample to determine baseline amounts. Blood and urine specimens are being analyzed for a number of different classes of substances, including metals, phthalates, polychlorinated biphenyls (PCBs), brominated flame retardants (BFRs), organochlorine pesticides, organophosphate insecticide metabolites, phenoxy herbicides, cotinine, perfluorinated compounds and bisphenol-A. The survey also includes a questionnaire, which allows for the analysis of risk factors related to exposure to these environmental chemicals.

Brominated flame retardants (BFRs) and phthalates are two types of chemicals that are increasingly found through biomonitoring. Some chemicals, such as polychlorinated biphenyls (PCBs), dioxins, and Polybrominated Diphenyl Ethers (PBDEs) are considered “persistent,” remaining in the body for long periods of time as they adhere to fatty tissue. Others, such as volatile organic compounds (VOCs) and phthalates are processed by the body and expelled through urine.